Bob,

It would be quick and easy to remove the locks and have a look inside.

From the picture of the top of the gun, from what I can see peeking out from underneath the lever, it appears the screw is not oriented correctly.
Is that an accurate perception or am I mistaken?
I can't imagine anyone assembling or reassembling the gun without it being oriented correctly.

Inspecting the backsides of the locks and toplever shaft would allow you to verify the numbers and look for any indication of reworking; bugered screws, pins, etc.
Just some thoughts that come to my mind. I would certainly be interested in others opinions.